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I am sure you won't get into any issues by keeping them both separate - but it doesn’t make any sense in doing that. You should definitely 301 redirect the old one .. page by page to the new site. It doesn’t make sense to keep them both and you will lose since Google might start to rank one page from the com.au and for another query one from net.au. They should for sure consolidate everything into one single side. Keeping them separately there migt also be some branding issues - as users might get confused. "oh, last time I was on the other Screento - let's look for those guys again" So, you won't get into issues from Google with Duplicate content or anything else but you might shoot yourself in the foot by not 301 redirecting the old pages to the new ones since you will compete with each other and it just doesn’t make sense to keep them both. So to make the long story short: Consolidate with 301 and you will be in good shape. Don't do it and you will be safe but you will lose on branding and rankings. Hope it helps.